From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 17408C5519F for ; Fri, 20 Nov 2020 15:00:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8EDCE22272 for ; Fri, 20 Nov 2020 15:00:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="W5Y9nvrd" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728076AbgKTPAb (ORCPT ); Fri, 20 Nov 2020 10:00:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36972 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727801AbgKTPAb (ORCPT ); Fri, 20 Nov 2020 10:00:31 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E70C8C0613CF for ; Fri, 20 Nov 2020 07:00:30 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=NiuizQJIYv9MbTQDyL6kr/KprFoXkhdzvZvshBrCr/c=; b=W5Y9nvrdN7SJJgjDkR857bMCI5 WgHN1yn81J7n4R9+szMLSLmcnueBnCeriem/X9E77Fyo7lEVbPZ07lRDMfAlChRRgeBKGwqc5bfct LLnxaiKkI6zv7oOZ784WCJYfOCPqkHFdboEpkz0F+l5ghqvPvM57ZT4gA/SITHMH++QiXCnBuf4Kx UMAi8saLKQE1xeDOIIV7D80RNnvq2lFflYqB0JUT8HOfOqyw6ddbLCzoAty4fhBrUpLAF7MqlxU2u 5WjZqhuqGlfe9gznf7/7Qr7PzDsWnu/wbk/Ma44+B95C5XvosCm2SHJnXd4hqshXaEz0rfjxjc6ei OG5ThHbg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kg7tg-00005F-Dg; Fri, 20 Nov 2020 15:00:24 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id CB369304D28; Fri, 20 Nov 2020 16:00:23 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id A770C20244762; Fri, 20 Nov 2020 16:00:23 +0100 (CET) Date: Fri, 20 Nov 2020 16:00:23 +0100 From: Peter Zijlstra To: Will Deacon Cc: linux-kernel@vger.kernel.org, kernel-team@android.com, Catalin Marinas , Yu Zhao , Minchan Kim , Linus Torvalds , Anshuman Khandual , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 4/6] mm: proc: Invalidate TLB after clearing soft-dirty page state Message-ID: <20201120150023.GH3040@hirez.programming.kicks-ass.net> References: <20201120143557.6715-1-will@kernel.org> <20201120143557.6715-5-will@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201120143557.6715-5-will@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 20, 2020 at 02:35:55PM +0000, Will Deacon wrote: > Since commit 0758cd830494 ("asm-generic/tlb: avoid potential double flush"), > TLB invalidation is elided in tlb_finish_mmu() if no entries were batched > via the tlb_remove_*() functions. Consequently, the page-table modifications > performed by clear_refs_write() in response to a write to > /proc//clear_refs do not perform TLB invalidation. Although this is > fine when simply aging the ptes, in the case of clearing the "soft-dirty" > state we can end up with entries where pte_write() is false, yet a > writable mapping remains in the TLB. > > Fix this by calling tlb_remove_tlb_entry() for each entry being > write-protected when cleating soft-dirty. > > @@ -1053,6 +1054,7 @@ static inline void clear_soft_dirty(struct vm_area_struct *vma, > ptent = pte_wrprotect(old_pte); > ptent = pte_clear_soft_dirty(ptent); > ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent); > + tlb_remove_tlb_entry(tlb, pte, addr); > } else if (is_swap_pte(ptent)) { > ptent = pte_swp_clear_soft_dirty(ptent); > set_pte_at(vma->vm_mm, addr, pte, ptent); Oh! Yesterday when you had me look at this code; I figured the sane thing to do was to make it look more like mprotect(). Why did you chose to make it work with mmu_gather instead? I'll grant you that it's probably the smaller patch, but I still think it's weird to use mmu_gather here. Also, is tlb_remote_tlb_entry() actually correct? If you look at __tlb_remove_tlb_entry() you'll find that Power-Hash-32 will clear the entry, which might not be what we want here, we want to update the entrty.